The present invention relates to a solar energy collecting panel and an apparatus for utilizing the solar energy collecting panel.
Various apparatus have been proposed for collecting heat energy from the sun. Many of these apparatus comprise heavy rigid boxes which are sealed from the outside and use the "greenhouse" effect to heat water passing through finned tubes and the like within the box. Other collectors focus sunlight on blackened or heat absorbing tubes to more efficiently heat the water therein.
A further solar collecting panel, for example, of the type disclosed in U.S. Pat. No. 3,991,742 issued Nov. 16, 1976 to Gerber, includes a lower layer and an upper heat absorbing layer with a spreader or separation member located therebetween. The spreader is provided to maintain separation between the two layers and to break up small rivulets of water to establish a thin sheet of water covering the entire surface of the panel layers. The separator may be fiberglas screening, plastic netting, open weave cloth, or open cell polyurethane foam plastic. The moving force on the water is primarily gravity and the input water is controlled to obtain an even flow rate through the entire panel. Another device of this general type for spreading water over the entire heat collecting surface is disclosed in U.S. Pat. No. 3,215,134 issued Nov. 2, 1965 to Thomason and includes a corrugated sheet to evenly distribute the water flowing along the sheet.
Other solar energy collecting devices have been proposed that utilize a fabric element which is directly heated by the sun. Water is then allowed to flow over the heated fabric to remove heat therefrom. Devices of this type generally required a bulky support frame and rely primarily on gravity to drive the water over the fabric element. Devices of this general type are disclosed in U.S. Pat. Nos. 4,129,117 issued Dec. 12, 1978 to Harvey; 4,175,542 issued Nov. 27, 1979 to Duchene; and 4,186,721 issued Feb. 5, 1980 to Whitman.
It will be appreciated that collectors of these types are generally expensive to produce and difficult to install. Further, heat transfer to the fluid is limited by the number of tubes that can be installed within the limited area of the box and still be exposed to sufficient sunlight.
It is therefore an object of the present invention to provide a lightweight highly efficient solar collecting panel which is simple in construction and easy to install.
A further object of the present invention is to provide a solar collecting panel which employs fibers for transporting fluid against a heat collecting surface by capillary action and surface tension. A collecting panel according to the present invention has the further object of establishing a controlled flow rate for the fluid through the fibers which flow rate is not dependent upon gravity as the sole driving force and does not require regulation of the input flow to the solar collecting panel.
Still a further object of the present invention is to provide a solar collecting apparatus that utilizes the solar collecting panel of the present invention.
These and other objects of the present invention are achieved by a solar energy collecting panel including a first layer comprised of heat absorbing material. Fibers are provided for repeatedly transporting fluid by capillary action toward a first surface of the heat absorbing layer to transfer heat from layer to the fluid. The fibers are arranged to intimately contact the first surface and are held in intimate contacting relationship with the first surface by a second layer arranged beneath the fibers.
According to a preferred embodiment of the present invention, the fibers are a nonwoven needle punched fabric comprised of continuous filaments of polyester or polypropylene. Further, according to the preferred embodiment, the heat absorbing layer comprises a flexible film of rubber which is bonded to the fabric. The second layer is preferably comprised of heat reflective material in order to maintain the heat absorbed within the fabric at a maximum.
A solar energy collecting apparatus according to the present invention includes an inlet header and an outlet header and means for supplying fluid to be heated to the inlet header. A first layer of heat absorbing material has a first end sealed to the inlet header and a second end sealed to the outlet header. Fibers for repeatedly transporting fluid toward a first surface of the heat absorbing layer and for transporting fluid from the inlet header to the outlet header are arranged between the first layer and a second layer which has first and second ends sealed to the inlet and outlet headers respectively. The fibers are arranged to intimately contact the first surface and extend beyond ends of the first and second layers into the interior of the inlet and outlet headers.
According to a further feature of the present invention, the longitudinal edges of the first and second layers are bonded together to ensure that fluid cannot leak from the longitudinal edges.